Pain in Emergency Department (ED) patients has, heretofore, been grossly under-managed and under-studied. Nurses have a significant role in ED pain management, which includes administering analgesics and monitoring beneficial and adverse outcomes of analgesic therapy. Yet, virtually no nursing research has been conducted on pain or analgesic therapy outcomes in ED patients. This double-blind, randomized clinical trial will test the effects of three analgesics, intravenous (IV) ketorolac 30 mg, IV morphine sulfate 5 mg, and IV morphine sulfate 10 mg in selected ED patients with acute pain. The study examines: (a) analgesic effects (i.e., summed pain intensity differences and use of rescue medications); (b) patient sedation levels; (c) patient satisfaction with pain treatment; and (d) cost of treatment. The study sample will be 336 English- and Spanish-speaking patients (112 in each of the three drug groups) who present to the ED in moderate to severe pain. Patients will rate their pain intensity immediately before and at nine subsequent times over three hours. Sedation will be assessed at the same times. After three hours, patients will be interviewed about their satisfaction with the pain treatment they received. Planned pairwise comparisons, using an overall one-way ANOVA design, will test differences between groups in "summed pain intensity differences" scores, levels of sedation, patient satisfaction, specific factors that could influence patient satisfaction, and costs of treatment. Mann-Whitney pairwise comparisons will test differences between groups in number of rescue medications used. Interview transcripts will be analyzed, using the constant comparative method, to identify themes derived from patients' evaluations of their pain treatment. This study will be the first comprehensive risk-benefit ratio analysis of analgesic treatment of ED patients in pain. It will generate knowledge directly applicable to nursing's role in ED pain management and provide direction to future nursing and multidisciplinary investigations of pain management in ED patients.